1. Field of the Invention
The present invention relates to fluid flow sensors and controllers and more particularly to multi-gas flow sensors and control devices which may have non-linear bypass attributes.
2. Discussion of Related Art
Wang, in U.S. Pat. No. 6,826,953, discloses an apparatus and method for measuring flow. The flow sensor includes a sensor conduit and a bypass having at least one capillary tube. At least one of the length, inside diameter, and cross-sectional shape of the sensor conduit is substantially equal to the corresponding length, inside diameter, and cross-sectional shape of the at least one capillary tube.
Lull et al., in U.S. Pat. No. 6,962,164, disclose a system and method for controlling a mass flow controller to have a constant control loop gain under a variety of different types of fluids and operating conditions, and for configuring the mass flow controller for operation with a fluid and/or operating conditions different from those used during production of the mass flow controller. The system and method further facilitates control by reducing the effects of hysteresis in solenoid-actuated devices by providing a non-operational signal to the solenoid-actuated device.
Wang et al., in U.S. Pat. No. 7,043,374, disclose an apparatus and method of obtaining at least one representation of a characteristic function of a sensor from a test fluid during calibration, and of employing the at least one representation to determine flow rates through the sensor during operation with an arbitrary fluid.